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Membranes, biological phospholipids

Figure 2.3 Schematic diagram of a phospholipid biological membrane (5-6 nm in width). Figure 2.3 Schematic diagram of a phospholipid biological membrane (5-6 nm in width).
B Roux, TB Woolf. Molecular dynamics of Pfl coat protein in a phospholipid bilayer. In KM Merz Ir, B Roux, eds. Biological Membranes A Molecular Perspective from Computation and Experiment. Boston Birkhauser, 1996, pp 555-587. [Pg.495]

Langmuir-Blodgett films (LB) and self assembled monolayers (SAM) deposited on metal surfaces have been studied by SERS spectroscopy in several investigations. For example, mono- and bilayers of phospholipids and cholesterol deposited on a rutile prism with a silver coating have been analyzed in contact with water. The study showed that in these models of biological membranes the second layer modified the fluidity of the first monolayer, and revealed the conformation of the polar head close to the silver [4.300]. [Pg.262]

There are other ways in which the lateral organization (and asymmetry) of lipids in biological membranes can be altered. Eor example, cholesterol can intercalate between the phospholipid fatty acid chains, its polar hydroxyl group associated with the polar head groups. In this manner, patches of cholesterol and phospholipids can form in an otherwise homogeneous sea of pure phospholipid. This lateral asymmetry can in turn affect the function of membrane proteins and enzymes. The lateral distribution of lipids in a membrane can also be affected by proteins in the membrane. Certain integral membrane proteins prefer associations with specific lipids. Proteins may select unsaturated lipid chains over saturated chains or may prefer a specific head group over others. [Pg.266]

Phospholipids e.g. form spontaneously multilamellar concentric bilayer vesicles73 > if they are suspended e.g. by a mixer in an excess of aqueous solution. In the multilamellar vesicles lipid bilayers are separated by layers of the aqueous medium 74-78) which are involved in stabilizing the liposomes. By sonification they are dispersed to unilamellar liposomes with an outer diameter of 250-300 A and an internal one of 150-200 A. Therefore the aqueous phase within the liposome is separated by a bimolecular lipid layer with a thickness of 50 A. Liposomes are used as models for biological membranes and as drug carriers. [Pg.12]

Phospholipids are a major component of all biological membranes together with glycolipids and cholesterol. Due to their polar nature, i.e. hydrophilic head and hydrophobic tail, phospholipids form in water vesicles or liposomes. [Pg.970]

Cholesterol is found in many biological membrane and is the main sterol of animal organisms. It is eqnimolar with phospholipids in membranes of liver cell, erythrocytes, and myelin, whereas in human stratum comeum it lies in the outermost layer of the epidermis... [Pg.170]

Koryta et al. [48] first stressed the relevance of adsorbed phospholipid monolayers at the ITIES for clarification of biological membrane phenomena. Girault and Schiffrin [49] first attempted to characterize quantitatively the monolayers of phosphatidylcholine and phos-phatidylethanolamine at the ideally polarized water-1,2-dichloroethane interface with electrocapillary measurements. The results obtained indicate the importance of the surface pH in the ionization of the amino group of phosphatidylethanolamine. Kakiuchi et al. [50] used the video-image method to study the conditions for obtaining electrocapillary curves of the dilauroylphosphatidylcholine monolayer formed on the ideally polarized water-nitrobenzene interface. This phospholipid was found to lower markedly the surface tension by forming a stable monolayer when the interface was polarized so that the aqueous phase had a negative potential with respect to the nitrobenzene phase [50,51] (cf. Fig. 5). [Pg.429]

The octanol-water partition model has several limitations notably, it is not very biological. The alternative use of liposomes (which are vesicles with walls made of a phospholipid bilayer) has become more widespread [149,162,275, 380—4441. Also, liposomes contain the main ingredients found in all biological membranes. [Pg.67]

There are no convenient databases for liposome log P values. Most measured quantities need to be ferreted from original publications [149,162,376,381-387,443], The handbook edited by Cevc [380] is a comprehensive collection of properties of phospholipids, including extensive compilations of structural data from X-ray crystallographic studies. Lipid-type distributions in various biological membranes have been reported [380,388,433]. [Pg.69]

Fig. 6.9 Characteristic structures of biological membranes. (A) The fluid mosaic model (S. J. Singer and G. L. Nicholson) where the phospholipid component is predominant. (B) The mitochondrial membrane where the proteins prevail over the phospholipids... Fig. 6.9 Characteristic structures of biological membranes. (A) The fluid mosaic model (S. J. Singer and G. L. Nicholson) where the phospholipid component is predominant. (B) The mitochondrial membrane where the proteins prevail over the phospholipids...
A BLM can even be prepared from phospholipid monolayers at the water-air interface (Fig. 6.10B) and often does not then contain unfavourable organic solvent impurities. An asymmetric BLM can even be prepared containing different phospholipids on the two sides of the membrane. A method used for preparation of tiny segments of biological membranes (patch-clamp) is also applied to BLM preparation (Fig. 6.10C). [Pg.450]

New developments in immobilization surfaces have lead to the use of SPR biosensors to monitor protein interactions with lipid surfaces and membrane-associated proteins. Commercially available (BIACORE) hydrophobic and lipophilic sensor surfaces have been designed to create stable membrane surfaces. It has been shown that the hydrophobic sensor surface can be used to form a lipid monolayer (Evans and MacKenzie, 1999). This monolayer surface can be used to monitor protein-lipid interactions. For example, a biosensor was used to examine binding of Src homology 2 domain to phosphoinositides within phospholipid bilayers (Surdo et al., 1999). In addition, a lipophilic sensor surface can be used to capture liposomes and form a lipid bilayer resembling a biological membrane. [Pg.103]

Griffith, O. H., P. J. Dehlinger, and S. P. Van. 1974. Shape of the hydrophobic barrier of phospholipids bilayers (Evidence for water penetration into biological membranes). J. Membr. Biol. 15 159-192. [Pg.210]

An important characteristic of mammalian 15-LOX is its capacity to oxidize the esters of unsaturated acid in biological membranes and plasma lipoproteins without their hydrolysis to free acids. Jung et al. [19] found that human leukocyte 15-LOX oxidized phosphatidylcholine at carbon-15 of the AA moiety. Soybean and rabbit reticulocyte 15-LOXs were also active while human leukocyte 5-LOX, rat basophilic leukemia cell 5-LOX, and rabbit platelet 12-LOX were inactive. It was suggested that the oxygenation of phospholipid is a unique property of 15-LOX. However, Murray and Brash [20] showed that rabbit reticulocyte... [Pg.807]

Macrocyclic compounds with ion-chelating properties occur naturally and often function as ionophores, translocating ions across biological membranes many of these compounds are small cyclic polypeptides. Some natural carboxylic polyethers are selective for Li+ and are, therefore, ionophores for Li+. Monensin, shown in Figure Id, is a natural ionophore for Na+ but it will also complex with Li+ and it has been shown to mediate the transport of Li+ across phospholipid bilayers [21]. It has been proposed that synthetic Li+-specific ionophores have a potential role as adjuvants in lithium therapy, the aim being to reduce the amount of... [Pg.6]

On the other hand, cellular membranes are composed of chiral molecules such as phospholipids and cholesterol, but the homochirality of these constituents is not obviously manifested in the membrane s structure. However, in certain cases biological membranes exhibit a distinct helical or twisted structure, which is a very conspicuous sign of the chirality of the supramolec-ular aggregate. These chiral supramolecular aggregates are the subject of this chapter. [Pg.282]

Hydration of phospholipid head groups is essential properties not only for stabilizing bilayer structures in an aqueous environment, but also for fusion or endocytosis of biological membranes including protein transfers [33-35]. Hydration or swelling behavior has only been studied by indirect methods such as X-ray diffraction [36], differential scanning calorimetry (DSC) [37], and H-NMR [38,39]. [Pg.134]

The studies on phospholipid bilayers with defined amounts of charged component are helpful to explain the partition characteristics in biological membranes. Liposome water partition data of propranolol in lipids from kidney epithelial cells (a common model system in pharmaceutical sciences for the uptake into the gastrointestinal tract) have been successfully described with partition models developed for pure bilayers or defined mixtures [159]. Since lipophilic cations and anions can be used as probes for the membrane potential, their interaction with microbial and mitochondrial membranes has been studied... [Pg.235]

Casadio, R., Venturoli, G. and Melandri, B. A. (1988). Evaluation of the electrical capacitance in biological membranes at different phospholipid to protein ratios -a study in photosynthetic bacterial chromatophores based on electrochromic effects, Eur. Biophys. J., 16, 243-253. [Pg.262]

Biological membranes consist of a bilayer of phospholipids in which membrane proteins are either embedded (integral proteins) or simply adsorbed (boundary proteins) (1) (Figure 1.). These systems fulfill a variety of functions oT basic importance. One of the most significant is the compartimentation via the formation of cells and cell subunits based on the self organization of membranes (hydrophobic effect (2j). [Pg.209]


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See also in sourсe #XX -- [ Pg.357 ]

See also in sourсe #XX -- [ Pg.357 ]




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